1. Field of the Invention
The present invention relates to a technique for subjecting semiconductors to each kind of annealing by irradiating the semiconductors with laser light.
2. Description of the Prior Art
Heretofore, techniques are known for subjecting semiconductors to each kind of annealing by irradiating the semiconductors with laser light. For example, the following techniques are known; a technique for transforming an amorphous silicon film (a-Si film) formed on a glass substrate by the plasma CVD into a crystalline silicon film by irradiating the amorphous silicon film with laser light; and an annealing technique after impurity ion doping, or the like. As each kind of annealing technique using such laser light and an apparatus for laser light irradiation, there is a technique described in Japanese Unexamined Patent Application No. Hei 6-51238 filed by the applicant of the present invention.
Since each kind of annealing treatment using laser light does not cause thermal damage to a base substrate, the treatment becomes a useful technique in the case where a material that is weak to heat such as a glass substrate or the like is used as the substrate. However, there is a problem in that it is difficult to keep the annealing effect on a constant level at all times. Further, when an amorphous silicon film is crystallized by irradiating the amorphous silicon film with laser light, it is difficult to constantly obtain a favorable crystallinity that is required. Thus, a demand has been made on a technique for stably obtaining a crystalline silicon film having a more favorable crystallinity.